I was in the Spirit on the Lord's day,
Revelation 1:10
Some make the error of thinking that the Lord's Day of Revelation is Sunday (1st day of the week).
But what does Scripture teach is the Lord's Day?
But the seventh day is the sabbath of the LORD thy God:
Exodus 20:10
For he has somewhere spoken of the seventh day in this way:
And God rested on the seventh day from all his works.
There remains, then, a Sabbath-rest for the people of God;
Hebrews 4:4,9 ESV/NIV